oa.ctrl.rf.compHouse = {
/**
 * Evaluate the user's answers for an en-bloc exercise  
 * 
 * @author Gerd Wagner
 * 
 * @param {number} k  The problem number within the current exercise.
 * @param {string} answer  The user's answer for the kth problem.
 */
  evaluate: function ( k, answer) {
    var percentageCorrect = 0,
        problem = oa.currentProblems[k];
    if (parseInt(answer) === problem.getCorrectAnswer()) {
      if (oa.attemptCounter <= 1) { 
        oa.correctAnswerCounter += 1;
        if (problem.isBasicProblem()) {
          i = problem.operands[0] * 10 + problem.operands[1];  
          oa.currentExercise.getBasicProblemStatistics()[i].correctCounter++;
        }
      }
      oa.view.showSmilingAri();
    } else {
      if (problem.isBasicProblem()) {
        i = problem.operands[0] * 10 + problem.operands[1];
        if (oa.currentExercise.getBasicProblemStatistics()[i].correctCounter > 0) {
          oa.currentExercise.getBasicProblemStatistics()[i].correctCounter--;
        }
      }
      oa.view.showDisappointedAri();
      oa.attemptCounter += 1;
    }
    percentageCorrect = (oa.learningUnitProblemCounter<=0) ? 0 : 
        Math.floor( oa.correctAnswerCounter / (oa.learningUnitProblemCounter*oa.currentProblems.length) * 100);
    oa.view.showPercentageCorrect( percentageCorrect);
  }
};